Resist composition and method for producing semiconductor device

ABSTRACT

A resist composition includes: a crosslinking material that is crosslinked in the presence of an acid; an acid amplifier; and a solvent.

RELATED APPLICATION DATA

This application is a division of U.S. patent application Ser. No.13/238,004 filed Sep. 21, 2011, the entirety of which is incorporatedherein by reference to the extent permitted bylaw. The presentapplication claims the benefit of priority to Japanese PatentApplication No. JP 2010-217862 filed on Sep. 28, 2010 in the JapanPatent Office, the entirety of which is incorporated by reference hereinto the extent permitted by law.

FIELD

The present technology relates to a resist composition that reduces asize of an opening of a pattern for forming a resist pattern in aproduction process of a semiconductor device, and a method for producinga semiconductor device using the resist composition.

BACKGROUND

Associated with the high integration of semiconductor devices in recentyears, the pattern size demanded in the production process is beingconsiderably miniaturized. In an ordinary production process of a finepattern or a fine impurity distribution, a resist pattern is formed bythe photolithography technique, and the resist pattern thus formed isused as a mask. For example, a fine pattern is formed by etching variouskinds of thin films on a substrate with the resist pattern thus formedused as a mask, and a fine impurity distribution is formed by ioninjection to the substrate with the resist pattern thus formed used as amask.

Upon forming the fine pattern, the photolithography technique isimportant. The photolithography technique contains processes of resistcoating, exposure and development. Miniaturization of a pattern with thephotolithography technique has been achieved mainly by decreasing theexposure wavelength. However, the decrease of the exposure wavelengthencounters technical limitation, and the production cost is increased bydecreasing the exposure wavelength. Thus, there is limitation indecreasing the exposure wavelength.

Under the circumstances, a method for producing a fine resist patternbeyond the limitation of the photolithography technique by exposure hasbeen proposed (see, for example, JP-A-2000-298356). In the method forproducing a resist pattern, a resist pattern having been produced by thephotolithography technique is subjected to an additional process,thereby further miniaturizing the resist pattern.

In the technique proposed in JP-A-2000-298356, a first resist layercapable of generating an acid is formed on a semiconductor substrate,and a first resist pattern is formed through exposure and development. Asecond resist layer capable of undergoing crosslinking reaction with theacid present on the first resist pattern is then formed. A crosslinkedlayer is then formed with the acid supplied from the first resistpattern at the portion where the second resist layer is in contact withthe first resist pattern. Thereafter, the portion of the second resistlayer that is not crosslinked is dissolved and removed with water or anaqueous solution of a water-soluble organic solvent, thereby forming asecond resist pattern. The process of forming the second resist patternis performed repeatedly, thereby forming a target resist pattern.

Specifically, upon patterning the first resist layer through exposure,an acid is generated at the portion of the first resist layer that isirradiated with light. Through catalytic reaction of the acid thusgenerated, the portion of the first resist layer that has the acidpresent therein becomes soluble in the developer solution. The portionof the first resist layer that has became soluble in the developersolution is removed in the development process, but the first resistlayer that is adjacent to that portion has a certain amount of the acidpresent therein. However, the reaction catalyzed with the acid does notproceed to an extent that the resist layer becomes soluble in thedeveloper solution, and thus the acid remains after the development.Consequently, the remaining portion of the first resist layer adjacentto the portion that has been removed through the development has theacid molecules present therein.

In the technique disclosed in JP-A-2000-298356, the second resist layercapable of undergoing crosslinking reaction in the presence of an acidis formed on the first resist pattern. The acid molecules remaining inthe first resist pattern are then diffused into the second resist layerby a method of heating or the like. According to the procedure, thesecond resist layer that is adjacent to the first resist layercontaining the acid molecules present therein is insolubilized throughthe crosslinking reaction.

In the technique, the portion of the second resist layer that hasundergone the crosslinking reaction remains mainly in the side wall ofthe opening of the first resist pattern, and thereby the size of theopening of the resist pattern may be further decreased.

SUMMARY

In the technique, however, a crosslinked layer is formed in the secondresist layer that is in contact with the first resist pattern, with theacid supplied from the first resist pattern. Accordingly, when theamount of the acid supplied from the first resist pattern is small, thecrosslinked layer may not formed sufficiently, and the opening may beinsufficiently miniaturized. In particular, associated with theincreasing demand of miniaturization of patterns, the size of theopening is further demanded to be miniaturized, and thus the techniquemay fail to achieve the sufficient miniaturization demanded.

Consequently, the technique of forming a miniaturized pattern throughformation of the crosslinking layer in the second resist layer with theacid supplied from the first resist pattern has such a problem that aminiaturized pattern may not be sufficiently formed due to shortage ofthe amount of the acid supplied from the first resist pattern.

Accordingly, there is a need for a resist composition and a method forproducing a semiconductor device that are capable of miniaturizing anopening of a resist pattern.

According to an embodiment of the present technology, there is provideda resist composition containing a crosslinking material that iscrosslinked in the presence of an acid, an acid amplifier, and asolvent.

According to another embodiment of the present technology, there isprovided a method for producing a semiconductor device, containing:forming a first resist pattern capable of supplying an acid, with afirst resist composition, on a semiconductor substrate; forming a secondresist layer by coating a second resist composition containing acrosslinking material that is crosslinked in the presence of an acid, anacid amplifier, and a solvent, on the first resist pattern; forming acrosslinked portion in the second resist layer by diffusing an acid fromthe first resist pattern into the second resist layer; and removing aportion of the second resist layer that is not crosslinked.

According to the resist composition of the embodiment of the presenttechnology, the crosslinking material that is crosslinked in thepresence of an acid and the acid amplifier are contained, and thereforeacid amplification reaction occurs with the acid amplifier in thepresence of the acid. Accordingly, the acid may be generated in anamount that is sufficient for crosslinking the crosslinking materialwith the action of the acid amplifier, irrespective of the amount of theacid that is present in advance. Consequently, a crosslinked layer canbe formed.

According to the method for producing a semiconductor device of theembodiment of the present technology, the first resist pattern supplyingan acid is formed, and the second resist composition is coated thereon.The second resist composition contains the acid amplifier, andtherefore, acid amplification reaction occurs with the acid amplifierbased on the acid supplied from the first resist pattern. The number ofthe acid molecules present in the second resist layer can be increasedthrough the acid amplification reaction. The crosslinking material thatis crosslinked in the presence of an acid included in the second resistcomposition forms a crosslinked portion with the acid supplied from thefirst resist pattern and the acid generated through the acidamplification reaction. At this time, the acid is present in thesufficient amount through the acid amplification reaction, and thus thecrosslinking amount of the second resist layer can be increased.Consequently, a finer opening pattern can be formed in a miniaturizationmethod by forming a crosslinked layer at a portion of the second resistthat is in contact with the first resist pattern, by supplying an acidfrom the first resist pattern.

According to the embodiments of the present technology, there areprovided the resist composition and the method for producing asemiconductor device that are capable of miniaturizing an opening of aresist pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C are illustrations for a process diagram showing anexample of a method for producing a semiconductor device according to anembodiment of the present technology.

FIGS. 2D to 2F are illustrations for a process diagram showing anexample of a method for producing a semiconductor device according to anembodiment of the present technology.

FIGS. 3A to 3E are SEM micrographs of specimens of resist patterns inExamples and Comparative Example.

DETAILED DESCRIPTION

Embodiments of the present technology are described below, but thepresent technology is not limited to the embodiments in any way.

The following description are made in the following order.

-   1. Embodiment of method for producing semiconductor device-   2. Examples of method for producing semiconductor device

1. EMBODIMENT OF METHOD FOR PRODUCING SEMICONDUCTOR DEVICE

An embodiment of a method for producing a semiconductor device of thepresent technology will be described.

FIGS. 1A to 1C show a process diagram showing an example of a method forproducing a semiconductor device according to the embodiment. FIGS. 1Ato 1C each are a cross sectional view showing a structure formed on asubstrate. In the following example, a case where the embodiment isapplied to a positive resist is described, but the embodiment may alsobe applied similarly to a negative resist.

[Method for Producing Semiconductor Device: First Step]

As shown in FIG. 1A, a first resist layer 12 containing a first resistis formed on a semiconductor substrate 11. The first resist supplies anacid from the interior of the resist layer by a heat treatment. Thefirst resist layer 12 may be formed, for example, by a spin coatingmethod or the like. For example, the first resist is spin-coated on thesemiconductor substrate 11, and the solvent contained therein isevaporated by heating to approximately from 70 to 120° C. for a periodof approximately 1 minute, thereby forming the first resist layer 12.The first resist layer 12 may have a thickness of approximately from0.04 to 5 μm.

For forming a pattern with the first resist composition, an activeenergy ray is radiated to the first resist layer 12 through a photomaskhaving a pattern to be transferred (the operation will be hereinafterreferred to as exposure). Examples of the active energy ray include ag-ray, an i-ray, a KrF (krypton fluoride) laser light, an ArF (argonfluoride) laser light, an F2 laser light, an EUV (extreme ultraviolet)ray, an X-ray and an electron beam. In the case where an electron beamis used, the first resist layer 12 may be scanned with the electron beamwithout a photomask.

The first resist composition is not particularly limited in structureand formulation, and may contain a component that generates an acid uponirradiation with an active energy ray. In alternative, a resistcomposition that contains an acid in advance may be used. Examples ofthe resist composition include compositions containing a novolak resinhaving a protective group, a polyhydroxystyrene resin, an acrylic resinor the like, to which an onium salt photo-acid generating agent, or thelike is added. The resist composition may contain a basic compounddepending on necessity for neutralizing a part of the acid generated.Preferred examples of an acid that is contained in the first resistcomposition in advance include low molecular weight organic acid, suchas a carboxylic acid. The formulation is an ordinary chemicallyamplified resist, but the embodiment is not limited thereto.

The first resist layer 12 is exposed, and then subjected to a heattreatment, which is referred to as a PEB (post exposure bake) treatment,depending on necessity. The heat treatment may be performed at atemperature of approximately from 60 to 145° C. for a period ofapproximately 1 minute. The resist may be enhanced in sensitivity andresolution characteristics by the treatment.

Subsequently, the portion of the first resist layer 12 that has beenirradiated with an active energy ray is removed by developing, forexample, with an aqueous solution of TMAH (tetramethylammoniumhydroxide) (concentration: 0.01 to 4% by mass). Thus, a prescribed firstresist pattern 13 as shown in FIG. 1B is formed.

After the development, the whole or part of the first resist pattern 13may be exposed again for further generating an acid in the resistpattern, depending on necessity. Furthermore, a heat treatment may beperformed again subsequent to the exposure.

In an ordinary chemically amplified resist, an acid derived from aphoto-acid generating agent is formed in the exposed portion. Theprotective group in the resin as a major component of the resist isdeprotected through catalytic reaction of the acid thus generated, andan organic acid, such as a carboxylic acid, is generated. The portionhaving the organic acid generated therein becomes soluble in an alkalinedeveloper solution, such as an aqueous solution of TMAH(tetramethylammonium hydroxide). Accordingly, the exposed portion isdissolved in the developer solution, thereby forming a resist patternwith the remaining portion.

In the side wall portion of the first resist pattern 13, a slight amountof an acid is generated through irradiation with light with a certainintensity. The resin component in the resist is deprotected with theslight amount of the acid, but the degree of deprotection isinsufficient, and the side wall portion is not dissolved in thedeveloper solution and remains as a resist pattern.

Accordingly, in the case where the first resist composition is anordinary chemically amplified resist, the acid exists locally in theside wall of the first resist pattern 13 as shown in FIG. 1B. In thefigures, the acid existing locally in the side wall of the first resistpattern 13 is expressed by a hydrogen ion (H⁺).

Subsequently, a second resist composition is coated on the first resistpattern 13 by a spin coating method or the like, thereby forming asecond resist layer 14 as shown in FIG. 1C. In the followingdescription, the second resist composition may be referred to as achemical shrink material in some cases. After coating, the chemicalshrink material maybe heated to 80 to 105° C. for approximately 1 minutedepending on necessity for evaporating the solvent.

In the portion of the second resist layer 14 that is in contact with theside wall of the first resist pattern 13, the number of the acidmolecules is increased through acid amplification reaction occurringwith the acid (H⁺) from the first resist pattern 13. A crosslinked layeris formed through crosslinking reaction caused by the acid from thefirst resist pattern 13 and the acid amplified therewith. The portion ofthe second resist layer 14 that is not crosslinked is removed.

Embodiments of Second Resist Composition

The second resist composition (i.e., the chemical shrink material)contains an acid amplifier that causes acid amplification reaction inthe portion in contact with the side wall of the first resist pattern13, a crosslinking material that is crosslinked in the presence of anacid, and a solvent.

The chemical shrink material forming the second resist layer 14desirably does not cause affect on the first resist pattern 13 uponcoating the chemical shrink material. The affect herein includesdissolution, swelling or the like of the first resist pattern, andchanges of the shape, property or the like of the first resist layer 13.

Accordingly, the chemical shrink material may be coated by using asolvent that does not cause dissolution or the like of the first resistpattern 13. Examples of the solvent include water, a mixed solvent ofwater and a water-soluble organic solvent, and a water-soluble organicsolvent or an organic solvent that does not cause affect on the firstresist pattern 13, which may be used solely or as a mixture thereof.

Examples of the water-soluble organic solvent include an alcohol, suchas ethanol, methanol and isopropyl alcohol, γ-butyrolactone, acetone andN-methylpyrrolidone. The water-soluble organic solvent may be mixeddepending on the solubility of the materials used as the second resistcomposition, in such a range that the first resist pattern 13 is notdissolved.

Examples of the organic solvent that does not cause affect on the firstresist pattern 13 include an alcohol solvent and an ether solvent, suchas ethanol, methanol, isopropyl alcohol and dimethyl ether, which may beused solely or as a mixture thereof.

The acid amplifier contained in the chemical shrink material may besoluble in the solvent, e.g., water, the mixed solvent of water and awater-soluble organic solvent or the organic solvent, and may cause acidamplification reaction in the solvent.

Examples of the acid amplifier soluble in the solvent include aninclusion complex of an acid amplifier such as a diol monosulfonate anda compound represented by the following general formula (1) and aninclusion compound represented by the following general formula (2).

The compound represented by the general formula (1) is the acidamplifier itself. In the case where R¹ is the substituent 1 in thegeneral formula (1), the compound iscis-3-(1-octanesulfonyloxy)-2-pinanol (AA1). In the case where R¹ is thesubstituent 2, the compound iscis-3-((+)-10-camphorsulfonyloxy)-2-pinanol (AA2). In the case where R¹is the substituent 3, the compound is(cis-3-(p-toluenesulfonyloxy)-2-pinanol (AA3). The compounds AA1 to AA3all have a sulfonyl group (—S(═O)₂—) in the substituent R¹. Thecompounds AA1 to AA3 are all insoluble in water.

The compound represented by the general formula (2) is an inclusioncompound. The compound of the general formula (2) is an example of acyclodextrin derivative, and a structure of methyl-β-cyclodextrin isshown. A cyclodextrin is one kind of a cyclic oligosaccharide thatcontains several D-glucose molecules bonded through α-1,4-glucoside bondto form a cyclic structure. For example, a compound containing sixglucose molecules bonded circularly is referred to as α-cyclodextrin, acompound containing seven glucose molecules bonded circularly isreferred to as β-cyclodextrin, and a compound containing eight glucosemolecules bonded circularly is referred to as γ-cyclodextrin.

A cyclodextrin has a hydrophobic interior and a hydrophilic exterior.Accordingly, a cyclodextrin itself is soluble in water, and has such aproperty that a hydrophobic compound soluble only in an organic solventis included in the cyclodextrin ring, thereby making the hydrophobiccompound water-soluble.

Upon adding AA1 to AA3 into an aqueous solution of a cyclodextrin, AA1to AA3, which are originally water-insoluble, are included in the cyclicstructure of a cyclodextrin and become water-soluble. In other words, aninclusion complex is produced with the acid amplifier as a guestmolecule and the inclusion compound as a host molecule, and thereby thewater-insoluble acid amplifier can be dissolved in an aqueous solvent.

In addition to the acid amplifiers and the inclusion compounds mentionedabove, examples thereof also include known acid amplifiers, such ascompounds (3) to (13) below, and inclusion compounds capable of forminga water-soluble inclusion complex with the acid amplifiers.

-   (3) cis-1-phenyl-2-(p-toluenesulfonyloxy)-1-cyclohexanol-   (4) cis-1-methyl-2-(p-toluenesulfonyloxy)-1-cyclohexanol-   (5) cis-1-methyl-2-(1-octanesulfonyloxy)-1-cyclohexanol-   (6) cis-1-methyl-2-((+)-10-camphorsulfonyloxy)-1-cyclohexanol-   (7) p-toluenesulfonyloxycyclohexane-   (8) p-toluenesulfonyloxycyclopentane-   (9) 1,3-di(p-toluenesulfonyloxy)cyclohexane-   (10) 1,4-di(p-toluenesulfonyloxy)cyclohexane-   (11) 3-phenyl-3,3-ethylenedioxy-1-propyl-p-toluene sulfonate-   (12) 4-(tert-butoxycarbonyloxy)benzyl-p-toluene sulfonate-   (13) tert-butyl-2-methyl-2-(p-toluenesulfonyloxymethyl)acetoacetate

In the case where an acid amplifier exhibits sufficient solubility in asolvent used, the acid amplifier may be used solely without forming aninclusion complex. For example, in the case where an acid amplifierexhibits sufficient solubility in an aqueous solvent, the acid amplifiermay be used solely without forming the inclusion compound.

The crosslinking material contained in the chemical shrink material maybe one kind or two or more kinds of crosslinking resins, one kind or twoor more kinds of crosslinking agents, or a mixture thereof. In the casewhere water or a mixed solvent of water and a water-soluble organicsolvent is used as the solvent, a water-soluble resin and awater-soluble crosslinking agent are preferably used.

Examples of the crosslinking resin include a polyvinyl acetal resin, apolyvinyl alcohol resin, a polyacrylic acid resin, anoxazoline-containing water-soluble resin, an aqueous urethane resin, apolyallylamine resin, polyethyleneimine resin, a polyvinylamine resin, awater-soluble phenol resin, a water-soluble epoxy resin, apolyethyleneimine resin and a styrene-maleic acid copolymer, which maybe used solely or as a mixture thereof. Examples of the crosslinkingagent include a melamine crosslinking agent, such as methylol melamineand methoxymethylol melamine, a urea crosslinking agent, such asmethoxymethylol urea and ethylene urea, and an amino crosslinking agent,such as isocyanate, benzoguanamine and glycoluril, which may be usedsolely or as a mixture thereof.

The crosslinking material is not limited to the resins and crosslinkingagents mentioned above, and a crosslinking agent and a crosslinkingresin having a crosslinking group that are soluble in the solvent usedand form crosslinking with the acid may be used. In the case of anaqueous solvent is used, in particular, any one of a water-solublecrosslinking agent that is soluble in the aqueous solvent and formscrosslinking with the acid, and a water-soluble resin having acrosslinking group that forms crosslinking with the acid may be used.

In the case where a mixture is used as the crosslinking material, asuitable formulation thereof may be determined depending on the firstresist composition used, the reaction conditions employed, and the like.

[Method for Producing Semiconductor Device: Second Step]

After forming the second resist layer 14 by coating the chemical shrinkmaterial, a heat treatment is performed for diffusing the acid in thefirst resist pattern into the second resist layer 14 (the treatment isreferred to as a mixing bake treatment). The conditions for the mixingbake treatment may be, for example, a temperature of from 70 to 150° C.for a period of approximately from 1 to 2 minutes.

The acid in the first resist pattern 13 is diffused into the layerformed of the chemical shrink material by the mixing bake treatment asshown in FIG. 2D. Upon diffusing the acid from the first resist pattern13 to the second resist layer 14, the acid amplifier contained in thechemical shrink material is decomposed through catalytic reaction of theacid thus diffused. According to the mechanism, an acid is generated inthe second resist layer 14 as shown in FIG. 2E. A detailed example ofthe reaction is shown in the reaction scheme (14) below.

In the reaction scheme (14), CF₃SO₃H is shown as an example of the aciddiffused from the first resist pattern 13 into the second resist layer14. In the second resist layer 14, the acid amplifier is decomposedthrough catalytic reaction of CF₃SO₃H to form a sulfonic acid (RSO₃H).

In the reaction, one sulfonic acid molecule forms another one sulfonicacid molecule without consuming the original sulfonic acid molecule.Accordingly, the number of sulfonic acid molecules is increased to twoin total. In the acid amplification reaction, the aforementionedreaction occurs as chain reaction, thereby increasing the amount of theacid.

In the mixing bake treatment, acid molecules are diffused into thechemical shrink material and cause the acid amplification reaction. Theacid functions as a catalyst to the acid amplifier through the mixingbake treatment, thereby inducing the acid amplification reaction. Theacid further induces the crosslinking reaction in the chemical shrinkmaterial, and the portion of the second resist layer that has the acidpresent therein becomes insoluble in various solvents.

In the case where the temperature range that is suitable for diffusingthe acid from the first resist layer 13 to the second resist layer 14 inthe mixing bake treatment is different from the temperature range thatis suitable for performing the acid amplification reaction afterdiffusing the acid, the temperature may be changed stepwise to thesuitable temperatures, thereby providing a favorable crosslinkedportion. In other words, the diffusion of the acid into the secondresist layer 14 and the acid amplification reaction in the second resistlayer 14 may be performed under conditions different from each other.

For example, the mixing base treatment for accelerating the diffusion ofthe acid from the first resist layer 13 to the second resist layer 14 asshown in FIG. 2D maybe performed as a first heat treatment, and a secondheat treatment for accelerating the acid amplification reaction in thesecond resist layer 14 as shown in FIG. 2E may be performed.

The first heat treatment for accelerating the diffusion of the acid maybe performed, for example, at a temperature of from 70 to 150° C. for aperiod of approximately from 1 to 2 minutes. Thereafter, the second heattreatment for the acid amplification reaction may be performed at atemperature of from 80 to 160° C. for a period of from 1 to 3 minutes.

The suitable temperature ranges in the first heat treatment and thesecond heat treatment may be arbitrary temperatures that correspond tothe materials used in the first resist composition and the chemicalshrink material. Even in the case where the first heat treatment and thesecond heat treatment are performed separately, it is considered thatthe diffusion of the acid and the acid amplification reaction occurcontinuously. Specifically, it is considered that the acid amplificationreaction occurs also in the heating within the temperature range for thefirst heat treatment, and the diffusion of the acid occurs also in theheating within the temperature range for the second heat treatment,whereby the diffusion and the reaction occur continuously.

In the second resist layer 14, the crosslinking material undergoescrosslinking reaction with the acid from the first resist pattern 13 andthe acid molecules thus amplified through the acid amplificationreaction. A crosslinked layer is formed through the crosslinkingreaction at the portion that is in contact with the side wall of thefirst resist pattern 13. The resist patterns are washed with a solventthat does not dissolve the first resist pattern 13. The non-crosslinkedportion of the second resist pattern 14 is dissolved and removed bywashing with the solvent.

According to the process steps thus performed, a second resist pattern15 is provided that is formed of the crosslinked layer of the chemicalshrink material and decreases the size of the opening of the firstresist pattern 13 as shown in FIG. 2F. Furthermore, the process steps offrom FIG. 1C to FIG. 2F may be performed repeatedly depending onnecessity, thereby forming a crosslinked portion of the chemical shrinkmaterial further on the second resist pattern 15, and thus a resistpattern having an opening that is further decreased in size may beprovided.

Upon forming the second resist pattern 15, the resist patterns may bewashed with water, a mixed solvent of water and a water-soluble organicsolvent, or an organic solvent that does not dissolves the first resistpattern 13. For example, a mixed solvent of water and isopropanol mixedto a concentration of approximately from 1 to 30% by mass may be usedfor washing. The non-crosslinked portion of the second resist 14 isdissolved, and thereby the second resist pattern 15 is provided that isformed of the crosslinked layer of the chemical shrink material anddecreases the size of the opening of the first resist pattern 13 asshown in FIG. 2F.

A semiconductor device may be produced in an ordinary method with thefirst resist pattern 13 and the second resist pattern 15 formed by theprocess steps of from FIG. 1A to FIG. 2F as a mask. For example, etchingof an underlayer, ion implantation, and the like may be performed withthe resist patterns as a mask, thereby producing a semiconductor device.

The miniaturization method of a pattern by forming a crosslinked layerin the second resist layer adjacent to the first resist pattern with anacid supplied from the first resist pattern has a problem of failing toachieve sufficient miniaturization due to shortage of the amount of theacid supplied. In the method for producing a semiconductor deviceaccording to the embodiment, on the other hand, the second resistcomposition (i.e., the chemical shrink material) containing an acidamplifier and a crosslinking material is used for forming the secondresist layer. The use of the chemical shrink material generates andsupplies a sufficient amount of an acid to the second resist layer.Accordingly, the second resist pattern having a sufficient thickness canbe formed from the second resist layer, and thereby an opening of aresist pattern having a shape that is further miniaturized as comparedto an ordinary one. Consequently, a semiconductor device having a shapeor an impurity distribution that is further miniaturized as compared toan ordinary one can be produced.

2. EXAMPLE OF METHOD FOR PRODUCING SEMICONDUCTOR DEVICE

The present technology will be described specifically below withreference to examples, in which a resist pattern was produced with thesecond resist composition (i.e., the chemical shrink material). In thefollowing example, only the formation of a resist pattern in theproduction of a semiconductor device is performed, and theminiaturization of the shape of the opening of the resist pattern thusformed is investigated.

[Formation of First Resist Pattern]

The first resist pattern used for evaluation of the second resistpattern of the examples was produced. The second resist patterns ofExamples and Comparative Example were formed on the first resist patternfor evaluation.

A resist pattern was formed with a resist for KrF lithography, P3593,available from Tokyo Ohka Kogyo Co., Ltd., which was a chemicallyamplified excimer resist, as the first resist composition.

The first resist composition was coated on a silicon wafer to athickness of 1.1 μm by a spin coating method, and subjected to aprebaking treatment at 100° C. for 60 second for evaporating thesolvent, thereby forming the first resist layer. The formation of thefirst resist layer was performed with Coater-Developer RF³, availablefrom Sokudo Co., Ltd.

The first resist layer thus formed was exposed by irradiating with KrF(krypton fluoride) excimer laser light having a wavelength of 248 nmwith FPA-6000ES6a, available from Canon, Inc., with conventionalillumination of NA (numerical aperture)=0.55 and σ=0.5.

After exposing, the first resist layer was subjected to a PEB treatmentat 110° C. for 60 seconds with Coater-Developer RF³.

Subsequently, the first resist layer was developed with a TMAH aqueoussolution having a concentration of 2.38% by mass by paddle development,and then subjected to a heat treatment at 100° C. for 90 seconds.According to the procedures, the first resist pattern as aline-and-space pattern with a pitch of 1.5 μm was produced. The firstresist pattern thus obtained had a space width (i.e., a width of theopening) of 0.5 μm and a resist width of 1.0 μm.

EXAMPLE 1 [Production of Second Resist Composition]

The second resist composition (i.e., the chemical shrink material) wasproduced.

In a 1-L measuring flask, 100 g of pure water was added to 100 g of a20% by mass solution of a polyvinyl acetal resin (S-Lec KW3 and KW1,available from Sekisui Chemical Co., Ltd.), and mixed under stirring atroom temperature for 6 hours, thereby providing a 10% by mass aqueoussolution of the polyvinyl acetal resin.

860 g of pure water and 40 g of IPA were mixed with 100 g ofmethoxymethylol melamine (Cymel 370, available from Mitsui Cyanamid,Ltd.), and mixed under stirring at room temperature for 6 hours, therebyproviding an approximately 10% by mass aqueous solution ofmethoxymethylol melamine.

200 g of the 10% by mass aqueous solution of the polyvinyl acetal resinand 40 g of the approximately 10% by mass aqueous solution ofmethoxymethylol melamine thus produced were mixed under stirring at roomtemperature for 6 hours, thereby providing a mixed aqueous solutionhaving a concentration of methoxymethylol melamine of 20% by mass withrespect to the polyvinyl acetal resin.

[Synthesis of Acid Amplifier AA1]

Synthesis Method of AA1: cis-3-(1-octanesulfonyloxy)-2-pinanol

In a four-neck flask, 2.0 g (11.8 mmol) of cis-2,3-pinandiol, 3 mL (0.02mol) of triethylamine and 20 mg (0.16 mmol) of 4-dimethylaminopyridinewere dissolved in 12 mL of chloroform, and the mixture was stirred for 1hour over an ice bath. A chloroform solution of 1-octanesulfonylchloride (2.52 g/10 mL) (11.8 mmol) was added dropwise thereto with adropping funnel, and the mixture was stirred at room temperature for 1day. Thereafter, iced water was added thereto, the mixture was stirredfor 1 hour, and the solution was extracted with chloroform. The organiclayer was rinsed with 2.4N HCl and a saturated sodium hydrogencarbonatesolution in this order, and dried over anhydrous magnesium sulfate, andthe solvent was distilled off under reduced pressure. The resultingliquid was purified by column chromatography (filler: silica gel (WakoGel C-200), developing solvent: ethyl acetate/n-hexane=1/4), therebyproviding 1.46 g of a yellow viscous liquid (yield: 36%).

The acid amplifier AA1 was thus synthesized in the aforementionedmanner.

[Production of Inclusion Complex ICAA1]

The acid amplifier AA1 was then included in methyl-β-cyclodextrin (MβCD)to prepare a water-soluble acid amplifier. Specifically, the acidamplifier AA1 was added to an aqueous solution of methyl-β-cyclodextrin(MβCD) at a molar ratio of MβCD/AA1 of 1/2, i.e., an excessive amount ofAA1, and the mixture was stirred for 12 hours. Thereafter, AA1 that wasnot included in MβCD but remained in the aqueous solution was removed byfiltration. Thereafter, the solvent was distilled off from the resultingaqueous solution containing the inclusion complex of AA1 included inMβCD, thereby preparing the inclusion complex in the form of a whitesolid.

The inclusion complex (ICAA1) of AA1 included in methyl-β-cyclodextrinwas thus prepared in the aforementioned manner.

[Formation of Second Resist Pattern]

A chemical shrink material of Example 1 was prepared by adding 40% bymass of the inclusion complex (ICAA1) to the mixed aqueous solutionhaving a concentration of methoxymethylol melamine of 20% by mass withrespect to the polyvinyl acetal resin.

The chemical shrink material of Example 1 containing the acid amplifierthus prepared was coated on the first resist pattern formed by using thechemically amplified excimer resist by a spin coating method at arotation number of 3,000 rpm for a period of 30 seconds. After spincoating, the solvent (water) was evaporated from the coated resist by aheat treatment at 100° C. for 60 seconds. The resist was then subjectedto a mixing bake treatment at 111° C. for 2 minutes, and then rinsedwith water for 30 seconds.

The second resist pattern of Example 1 was thus formed in theaforementioned manner.

EXAMPLE 2

The acid amplifier AA2 was synthesized in the following manner, and aninclusion complex ICAA2 of AA2 included in methyl-β-cyclodextrin wasproduced in the same manner as in Example 1 except that AA2 was usedinstead of AA1.

The second resist composition (i.e., the chemical shrink material)containing ICAA2 was produced, and the second resist pattern of Example2 was formed, in the same manner as in Example 1 except that theconditions of the mixing bake treatment were changed. The mixing baketreatment in Example 2 was performed at 111° C. for 1 minute.

[Synthesis of Acid Amplifier AA2]

Synthesis Method of AA2: cis-3-((+)-10-camphorsulfonyloxy)2-pinanol

1.0 g (5.9 mmol) of cis-2,3-pinandiol, 1.5 mL of triethylamine and 20 mgof 4-dimethylaminopyridine were dissolved in 6 mL of dichloromethane,and the mixture was stirred over an ice bath. A solution of 1.5 g (5.9mmol) of (+)-10-camphorsulfonyl chloride dissolved in 5 mL ofdichloromethane was added dropwise thereto. The resulting solution wasstirred at room temperature for 2 days. After confirming that no furtherreaction proceeded by 1H-NMR, crashed ice was added thereto and stirredfor 1 hour. The solution was extracted with dichloromethane. The organiclayer was rinsed with 2.4N HCl and then with a saturated sodiumhydrogencarbonate solution, and dried over anhydrous magnesium sulfate,and the solvent was distilled off under reduced pressure. The resultingliquid was purified by column chromatography (filler: silica gel (WakoGel C-200), developing solvent: hexane/ethyl acetate=4/1), therebyproviding 0.73 g of colorless crystals (yield: 32%).

The acid amplifier AA2 was thus synthesized in the aforementionedmanner.

EXAMPLE 3

The acid amplifier AA3 was synthesized in the following manner, and aninclusion complex ICAA3 of AA3 included in methyl-β-cyclodextrin wasproduced in the same manner as in Example 1 except that AA3 was usedinstead of AA1.

The second resist composition (i.e., the chemical shrink material)containing ICAA3 was produced, and the second resist pattern of Example3 was formed, in the same manner as in Example 1.

[Synthesis of Acid Amplifier AA3]

Synthesis Method of AA3: cis-3-(p-toluenesulfonyloxy)-2-pinanol

In a four-neck flask, 1.5 g (9 mmol) of cis-2,3-pinandiol, 1.37 g (14mmol) of triethylamine and 0.3 g (2.5 mmol) of 4-dimethylaminopyridinewere dissolved in 25 mL of chloroform, and the mixture was stirred for 1hour over an ice bath. A chloroform solution of p-toluenesulfonylchloride (1.9 g/8.3 mL) (10 mmol) was added dropwise thereto with adropping funnel, and the mixture was stirred at room temperature for 1day. Thereafter, iced water was added thereto, the mixture was stirredfor 1 hour, and the solution was extracted with chloroform. The organiclayer was rinsed with 2.4N HCl, a saturated sodium hydrogencarbonatesolution and a saturated sodium chloride aqueous solution in this order,and dried over anhydrous magnesium sulfate, and the solvent wasdistilled off under reduced pressure. The resulting solid was purifiedby column chromatography (filler: silica gel (Wako Gel C-200),developing solvent: ethyl acetate/n-hexane=1/4), thereby providing 0.44g of a white solid (yield: 15%).

The acid amplifier AA3 was thus synthesized in the aforementionedmanner.

EXAMPLE 4

The second resist pattern of Example 4 was formed by using the secondresist composition (i.e., the chemical shrink material) produced inExample 1, in the same manner as in Example 1 except that the conditionsof the mixing bake treatment were changed. The mixing bake treatment inExample 4 was performed at 111° C. for 2 minutes for the first heattreatment, and further performed at 120° C. for 1 minute for the secondheat treatment for accelerating the acid amplification treatment.

COMPARATIVE EXAMPLE 1

A second resist composition (i.e., a chemical shrink material) ofComparative Example 1 was produced, and the second resist pattern ofComparative Example 1 was formed, in the same manner as in Example 1except that the acid amplifier was not added to the chemical shrinkmaterial.

[Results]

The resist patterns of Examples 1 to 4 and Comparative Example 1 weremeasured for the space width of the opening.

The space width of the opening of the first resist pattern beforeforming the second resist pattern was 0.50 μm.

The space width of the opening of the resist pattern having the secondresist pattern formed in Example 1 was 0.24 μm. Accordingly, theshrinking amount of the opening of the resist pattern with the secondresist pattern in Example 1 was 260 nm in total of both sides.

The space width of the opening of the resist pattern having the secondresist pattern formed in Example 2 was 0.26 μm. Accordingly, theshrinking amount of the opening of the resist pattern with the secondresist pattern in Example 2 was 240 nm in total of both sides.

The space width of the opening of the resist pattern having the secondresist pattern formed in Example 3 was 0.24 μm. Accordingly, theshrinking amount of the opening of the resist pattern with the secondresist pattern in Example 3 was 260 nm in total of both sides.

On the other hand, the space width of the opening of the resist patternhaving the second resist pattern formed in Comparative Example 1 was0.48 μm. Accordingly, the shrinking amount of the opening of the resistpattern with the second resist pattern in Comparative Example 1 was 20nm in total of both sides.

It is understood from the results that the use of the acid amplifiercontained in the second resist composition forms the second resistpattern that has a sufficiently large thickness as compared to anordinary chemical shrink material. Accordingly, an opening of a resistpattern that is further minute as compared to an ordinary one can beproduced.

The space width of the opening of the resist pattern having the secondresist pattern formed in Example 4 was 0.20 μm. Accordingly, theshrinking amount of the opening of the resist pattern with the secondresist pattern in Example 4 was 300 nm in total of both sides.

It is understood from the results that the second resist pattern ofExample 4 provides a larger shrinking amount than Examples 1 to 3 andComparative Example 1. In Example 4, the first heat treatment wasperformed as the mixing bake treatment, and the second heat treatmentwas performed for accelerating the acid amplification reaction.Accordingly, it is considered that in the process step of forming thecrosslinked layer in the second resist layer, the diffusion of the acidand the acid amplification reaction are performed at temperatures thatare controlled to the suitable ranges respectively, and thereby afavorable crosslinked portion can be provided.

FIGS. 3A to 3E are SEM micrographs of specimens of the resist patternsin Examples 1 to 3 and Comparative Example 1 and a specimen of the firstresist pattern before forming the second resist pattern. The SEMobservation of the resist pattern specimens was performed with SEMS3400, available from Hitachi High-Technologies Corporation.

FIG. 3A shows the resist pattern after treating with the chemical shrinkmaterial containing ICAA1 in Example 1. FIG. 3B shows the resist patternafter treating with the chemical shrink material containing ICAA2 inExample 2. FIG. 3C shows the resist pattern after treating with thechemical shrink material containing ICAA3 in Example 3. FIG. 3D showsthe resist pattern after treating with the chemical shrink materialcontaining no acid amplifier in Comparative Example 1. FIG. 3E shows theresist pattern before treating with the chemical shrink material as areference example.

In the resist pattern of Comparative Example 1 with no acid amplifiershown in FIG. 3D, the line width of the resist portion was thickened,and the width of the opening was decreased thereby, as compared to theresist pattern before treating with the chemical shrink material asshown in FIG. 3E. This is a result showing the miniaturization of theopening of the resist pattern obtained by using an ordinary chemicalshrink material.

In the resist patterns of Examples 1 to 3 formed by using the chemicalshrink materials containing the acid amplifiers AA1 to AA3 respectively,on the other hand, the opening of the resist pattern is furtherminiaturized as compared to the resist pattern of Comparative Example 1.

The use of a chemical shrink material containing an acid amplifier and acrosslinking material in the second resist layer generates and suppliesan acid in a sufficient amount to the second resist layer. Accordingly,the second resist pattern with a sufficient thickness can be formed fromthe second resist layer, and thereby a semiconductor device having afurther minute shape or impurity distribution as compared to an ordinaryone can be produced.

The aforementioned embodiment describes the structure where the secondresist pattern is formed on the side wall of the first resist pattern,but the portion where the second resist pattern is formed is notparticularly limited. For example, the second resist pattern may beformed on the upper portion of the first resist pattern.

The present technology is not limited to the constitutions described inthe aforementioned embodiments and examples, and various modifications,combinations and alternations may be made therein unless they deviatefrom the gist of the present technology.

The present disclosure contains subject matter related to that disclosedin Japanese Priority Patent Application JP 2010-217862 filed in theJapan Patent Office on Sep. 28, 2010, the entire content of which ishereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A method for producing a semiconductor device,comprising: forming a first resist pattern capable of supplying an acid,with a first resist composition, on a semiconductor substrate; forming asecond resist layer by coating a second resist composition containing acrosslinking material that is crosslinked in the presence of an acid, anacid amplifier, and a solvent, on the first resist pattern; forming acrosslinked portion in the second resist layer by diffusing an acid fromthe first resist pattern into the second resist layer; and removing aportion of the second resist layer that is not crosslinked.
 2. Themethod for producing a semiconductor device according to claim 1,wherein the crosslinked portion is formed in the second resist layer bya first heat treatment for diffusing the acid from the first resistpattern into the second resist layer and a second heat treatment foracid amplification reaction with the acid amplifier in the second resistlayer.
 3. The method for producing a semiconductor device according toclaim 2, wherein the first heat treatment is performed at a temperatureof from 70 to 150° C., and the second heat treatment is performed at atemperature of from 80 to 160° C.